Structure of Micelles of a Nonionic Block Copolymer Determined by SANS and SAXS

Abstract

The micellar state of Pluronic P123, which is a poly(ethylene oxide)-b-poly(propylene oxide)-b- poly(ethylene oxide) block polymer (EO(20)PO(70)EO(20)), has been investigated using SANS, SAXS, and differential scanning calorimetry under the conditions utilized in the synthesis of ordered mesoporous materials, such as SBA-15. The absolute intensity measurements, both with SANS and SAXS, have provided a detailed quantitative description of the P123 micelles in the framework of a simple core-shell spherical model. The model developed has been used to establish the structure of the copolymer micelles, including their size, shape, aggregation number and detailed composition, as well as the structural changes induced by varying reaction conditions. The effects of temperature, pH, acidic source and the addition of swelling agents (toluene and TMB) are reported and discussed.

Probing competitive interactions in quaternary formulations

“…These estimates of the aggregation numbers are entirely consistent with the measured P123 diffusion rates. [34] and Soni et al [40] b: Micelles number density value is in good agreement with the values reported by Manet et al [41] Significant changes in micelle morphology are observed when small molecule surfactants are added to the P123/alcohol systems. Take for example the SDS case, on addition of 50 mM SDS to the 5 wt% P123 aqueous and alcohol/aqueous solutions, Figure 3, SANS data show significant loss in the scattering intensity and the emergence of correlation peaks at higher Q values which together indicates the formation of smaller, mixed, charged micelles.…”

A Reliable Method for the Preparation of Multiporous Alumina Monoliths by Ice-Templating

“…They showed that the overall size of P123 micelles increase following the Hofmeister anions series due to their salting-in/out properties: NO 3´< Br´< Cl´< SO 4 2´< H 2 PO 4´ [ 37]. The salting-out ions Cl´, SO 4 2´a nd H 2 PO 4´d o not show a specific tendency to confine within the micelles.…”

“…Therefore micelle sizes in their presence are similar. As¨NO 3´i s a salting-in ion, its concentration in the outer shell of P123 micelles-composed of hydrophilic EO blocks-should be higher than in the bulk solution [37,38], whereas the concentration of salting-out ions is homogeneous. Ordered mesoporous alumina are thought to form through interactions between charged alumina colloids and the EO blocks of the surfactant [39].…”

Solubilisation of oils in aqueous solutions of a random cationic copolymer

“…[8,9] In particular, Pluronics have found a niche in this area. [9,10] Pluronics are commericaly available block copolymers of poly 15 (ethylene oxide) and poly(propylene oxide). Pluronic P123, for instance, is used to sythesise SBA-15 mesoporous silica.…”

“…[8] The initial structure of polymer micelles and their modification (by temperature, pH and solubilisation of hydrophobic oils) strongly impact the final mesoporous structure of hybrid materials. [9,10] Other common applications of Pluronics in-20 clude detergency, emulsification and fermentation. [11,12] For this reason, there is an abundance of literature dealing with solubilisation by Pluronics.…”